Kunihide Takahashi

Soil respiration in Siberian taiga ecosystems with different histories of forest fire.

Abstract Soil respiration includes soil microbial respiration, soil fauna respiration, and plant root respiration, therefore it reflects the biological activity of the soil ecosystems. The Siberian Taiga often experiences serious damage from forest fire, due to the very low precipitation in spring. We measured the soil respiration in five forest soil ecosystems with different histories of forest fire in Yakutsk in August 1997. The dominant tree species was Larix cajanderi, and the soils were Spodosols with a sandy and loamy texture. We also measured the soil respiration in a grassland. At severely burned sites, almost all the trees had fallen, litter and vegetation on the forest floor had burned, other forms of vegetation, including bryophytes or herbs, had invaded. At less severely burned forest sites, the trees were still standing but litter and vegetation on the forest floor had disappeared. Soil temperature, moisture, pH, and EC all increased after severe forest fires, the A-horizon showed a higher organic carbon content and a lower CN ratio. Soil respiration rate ranged from 18 to 397 (10-6 g CO2 m-2 s-1) in the same order reported so far. Soil respiration in severely burned forests was significantly lower than in intact forests, and was similar to that of grassland. Furthermore, mildly burned forests showed soil respiration values intermediate between those of severely burned and intact forests. These findings suggest that tree root respiration is considerably higher than root respiration of other plants or microbial and fauna respiration in soil. Soil microbial respiration was determined by the incubation method under the same temperature and soil moisture conditions as those in situ. Multiple regression analysis for mineral soils showed that the soil microbial respiration increased with the increase of the soil temperature and organic carbon content, that the soil microbial respiration decreased with the increase of pH. Whole soil microbial respiration within 1 m depth was higher in severely burned forests than in intact forests. These findings show that forest fire increased the soil microbial respiration and confirm that the loss of tree root respiration was the main reason for the decrease in soil respiration after severe forest fire. The contribution of tree root respiration to soil respiration was estimated to exceed 50%. Severe forest fire kills trees, and consequently results in a decrease of soil respiration.

Highly oxidized cuparene-type sesquiterpenes from a mycelial culture of Flammulina velutipes.

Cuparene-type sesquiterpenes were isolated from a culture broth of Flammulina velutipes (Curt.:Fr.) Sing. Using spectroscopic methods (HR-MS, 1H and 13C NMR, and 2D NMR, spectroscopy), their structures were determined to be 2,3,4,5-tetrahydro-2,7-dihydroxy-5,8,10,10-tetramethyl-2,5-methano-1- benzoxepin and 5-methyl-2-(3-oxo-1,2,2-trimethylcyclopentyl)benzoquinone. Both showed antimicrobial activity against Cladosporium herharum and Bacillus subtilis.

Lignin-degrading ability of litter-decomposing basidiomycetes from Picea forests of Hokkaido

The frequency of occurrence of the litter-decomposing basidiomycetes ofPicea abies andP. glehnii forest floors in Hokkaido was investigated. In both theP. abies andP. glehnii forest plots (each 10 m×10 m), litter-decomposing basidiomycetes of the generaCollybia andMycena were frequently observed. Species composition, frequency of occurrence, and basidioma numbers of each species were different between the two forest plots, but several species were common to both. Seven species isolated from theP. glehnii forest plot (C. acervata, C. pinastris, Marasmius pallidocephalus, Ma. wettsteinii, My. aurantiidisca, My. clavicularis, Mycena sp. 1) and four species from theP. abies forest plot (C. pinastris, My. alphitophora (=My. osmundicola), Mycena sp. 1,My. vulgaris) were tested for their ability to degrade lignin by a simple plate test for extracellular phenoloxidases and by measuring Klason lignin loss from needle litter of spruce. All the strains of the litter-decomposing fungi tested showed positive reactions on the plate test. Lignin contained in the needle litter was degraded by all strains tested (onlyMy. alphitophora was not tested), and rates varied from 9% to 40% over a two-month period in vitro. Seven species with ligninolytic ability in theP. glehnii forest plot and four such species in theP. abies forest plot were found respectively in 77% and 60% of the 100 subplots in each plot. The results of this study suggest that lignin decomposition of needle litter by litter-decomposing basidiomycetes in the forest floor is a common event in the studiedPicea forests of Hokkaido and that the diversity of the ligninolytic activity among the species or strains may cause spatial heterogeneity of litter decomposition in thePicea forest floor.

The occurrence and diversity of ectomycorrhizas of Larix kaempferi seedlings on a volcanic mountain in Japan

Larix kaempferi seedlings, in the process of becoming established during the revegetation process following a volcanic eruption, were assessed for the types, occurrence patterns and diversity of their ectomycorrhizas along an elevation gradient. On the basis of macro- and microscopic characteristics, 12 types of ectomycorrhizas were classified. In general, ectomycorrhizal types differed more by site than by seedling age. The majority of root systems of seedlings with an age ranging from 1 to 5 years were colonized by 1 or 2 types of mycorrhizal fungi at low and intermediate elevations, 2 or 3 types at a higher elevation. Under the more stressed environments of high and intermediate elevations, the mean d.w. of 1 yr old seedlings, 40% of which were colonized by 3 or 4 mycorrhizal fungi, was double the weight of the same aged seedlings at lower elevation sites, only 10% of which were colonized by 3 or 4 mycorrhizal fungi. The correspondence between the type and frequency of mycorrhizas, the elevation gradient and litter accumulation suggests that change in litter accumulation along gradient may influence not only mycorrhizal types and their occurrence, but also the diversity of mycorrhizas on one seedling. Diversity of mycorrhizas on the same seedling is assumed to be critical for the establishment of seedlings from the very beginning on stressed sites, and may also be influenced by the availability of nutrients. The more intensive competition between mycorrhizas that occurs due to a reduction in the food source (tip roots) shared by the mycorrhizal fungi with similar resource requirements, results in frequent co-occurrence of mycorrhizas in the same root system or even the same root tip. As a result, the diversity of mycorrhizal types seems to become simplified as the seedlings age.

Changes in net ecosystem production associated with forest fire in taiga ecosystems, near Yakutsk, Russia

Abstract Boreal and Taiga forests in Russia play an important role in carbon storage in terrestrial ecosystems. In this region, forest fires often occur, which affect considerably carbon cycling in the Taiga ecosystems. We estimated the net ecosystem production (NEP) in five ecosystems with different histories of forest fire in Yakutsk, Russia. The NEP was calculated as the difference between the net primary production (NPP) and annual soil organic matter decomposition (OMD). Severe burning and forest regeneration strongly affected OMD, NPP, and NEP. The NEP values were +1.24 and +1.40 Mg C ha−1 year−1 in two intact larch forests. But, the NEP values decreased to −0.89 and +0.07 Mg C ha−1 year−1 at two sites burned 5 years before. However, NEP showed the highest value, +2.39 Mg C ha−1 year−1, in a young larch forest burned 25 years before. The changes in NPP were considered to be a predominant factor for the changes in NEP in this region. Further studies should be carried out to analyze and / or estimate the changes in NPP after forest fire in relation to NEP in this region.

Effect of thinning on allometry and needle-age distribution of trees in natural Abies stands of northern Japan

We tested the effects of thinning on allometry and needle-age distribution in natural stands of Abies sachalinensis Masters by comparing a thinned stand to an unthinned, control stand. Specifically, we attempted to clarify how allometry was altered after a thinning. We assumed that the needle-age distribution of trees in the thinned stand would show a younger composition than in the control stand, given the effect of improved light conditions on needle dynamics following a thinning. These investigations were conducted in dense Abies stands located in central Hokkaido, northern Japan, 19 years post-thinning. In the thinned stand, the ratio of individual needle mass to stem mass increased significantly, as compared to the control. A difference in the H–DBH relationship between the stands was probably related to this tendency. Mean needle age of trees differed significantly between the two stands, and the thinned stand showed a younger needle age than the control. Within each stand, dominant trees showed older mean needle age than codominant or suppressed trees. These tendencies may have been caused by differential needle dynamics affected by light conditions in the stands, and by different crown positions among the trees within a stand. In summary, trees in the thinned stand showed increased growth rates after thinning, which were caused by increased needle mass, younger composition of needles, and improved light conditions.

Stand and self‐thinning dynamics in natural Abies stands in northern Hokkaido, Japan

Stand dynamics and self-thinning were analyzed in relation to the dynamics of above-ground biomass in natural Abies sachalinensis stands growing on sand dunes in northern Hokkaido, Japan. This was done in order to examine wave-type regeneration in the stands. Fifty-two plots were established in almost pure Abies stands that ranged from saplings to the mature and collapsing growth stages. Above-ground biomass and tree height reached asymptotic levels prior to the collapsing phase, unlike wave-regeneration Abies stands in central Japan and North America. Stand density was high in the young growth stages, but the self-thinning rate, that is, the density decrease per biomass growth in the study stands was greater than in wave-regeneration stands in central Japan, as indicated by a large self-thinning exponent (−1.26 by reduced major axis regression). The range of tree height distribution was very narrow, and the stands’ vertical structure was typically single-layered. The slenderness ratio of trees was large, except in young stands. In mature and collapsing stands, advanced seedling density increased markedly. These stand and tree characteristics were considered to be correlated with the wave-type regeneration in the study stands, and it is assumed that prevailing winds affect tree mortality.

Collybia biformis and C. pinastris new to Japan

Two species ofCollybia are recorded for the first time from Japan:C. biformis from Hokkaido, andC. pinastris from Hokkaido and Honshu (Nagano Prefecture). Macro- and microscopical descriptions and illustrations are provided for each species.

Notes on three species of Mycena new to Japan from Picea forests of Hokkaido

Three species ofMycena, viz.M. aurantiidisca, M. clavicularis, andM. oregonensis are recorded for the first time in Japan. Macro- and microscopical descriptions and illustrations are given for each species.

First Report on Racodium therryanum Associated with Seed Infection of Abies koreana in Korea

Racodium therryanum from Korea is described here for the first time. This fungus is characterized by that it is isolated from conifer seeds and seedlings, including Abies, colonies are dark green to dark gray and intricate, and it forms chlamydospores in cultures. This pathogenic fungus was isolated from seeds of Abies koreana growing on Mt. Halla, Jeju island. The fungus stopped growth more than at but grew even at . This fungus infected seeds of A. koreana under the snow during winter season. There is a high probability that this fungus affects the natural regeneration of A. koreana on Mt. Halla.